San Francisco officials simulated a series of terrorist attacks Wednesday, with one scenario including a suicide bomb aboard a Muni bus, to test the city's emergency preparedness skills.

The drill, organized by the city's Office of Emergency Services and Homeland Security, was part of a continuing series of exercises to assess the city's ability to respond to multiple incidents in a relatively short period of time -- figuring out everything from securing ambulances from neighboring counties, preserving evidence from the crime scenes, reuniting frantic parents with their school-age children and providing medical treatment for hundreds of people.

"We had a very successful exercise, and I say successful because not everything went exactly as we anticipated," said Mayor Gavin Newsom. "To me, that's success, that's the purpose of this. If everything went perfectly, then we frankly wouldn't have needed to do it, and we wouldn't have learned much."

Given the heightened public awareness arising from Hurricane Katrina, the Indian Ocean tsunami and the terror attacks on the London transit system, Newsom has been eager to publicize his administration's activities preparing for disasters, both manmade and natural.

The simulated drill started with a suicide bombing aboard a Muni bus at Fourth and Mission streets at 7:30 a.m. during the morning commute. Under the scenario, there were four fatalities. That was followed by an outdoor bomb an hour later at Pine and Montgomery streets in the Financial District in which 200 people were killed. Around 11:30 a.m., police stopped a van with explosives on the 500 block of O'Farrell Street in the Tenderloin and shot both the occupants. In addition, a suspicious package was reported at City Hall, which ended up being a false alarm.

During the exercise, officials "closed" the Bay and Golden Gate bridges and dealt with 619 people with injuries at area hospitals and health clinics. The drill also tested the city's emergency communications system.

In all, more than 200 people -- firefighters, police officers and workers from the Municipal Railway, the Department of Public Health and traffic control, among others -- were involved. The FBI also was on hand.

Most of the incidents were mental exercises in which the fire and police chiefs, the mayor and their deputies were presented with different scenarios and had to figure out how to respond and direct crews on the ground. Others were more hands-on. For example, a burnt-out bus -- made to represent the one hit by the suicide bomber -- was parked at the Hunters Point Naval Shipyard, and emergency workers were sent there to test their response.